Preparation of rolls for use in rod rolling mills



April 6, 1957 w. E. BRADBURY 2,788,717

PREPARATION OF ROLLS FOR USE IN ROD ROLLING MILLS Filed June 4, 1951 3 Sheets-Sheet 1 INVENTOR! 1 HOV/mm Z". fi/wabu/y April 6, 1957 w. E. BRADBURY 2,788,717

PREPARATION OF ROLLS FOR USE IN ROD ROLLING MILLS Filed June 4, 1951 v 3 sheets sheet 2 r w /2 k 22 /0 v 7. '40 TCJ} m wmv Il b II! I ,1 In. I gv/lgzflwlllllq l..\. i///// '9' I 22f 22C INVENTOR.

if w r4770 NEX April 16, 1957 w. E. BRADBURY 2,788,717

PREPARATION OF ROLLS FOR uss IN ROD ROLLING Mms F'i led June 4, 1951 3 Shee'ts-Sheet'5 United States raremo PREPARATION OF ROLLS FOR USE IN ROD ROLLING MILLS William Edward Bradbury, Kansas City, Kans., assignor, by mesne assignments, to Armco Steel Corporation, a corporation of Ohio Application June 4, 1951, Serial No. 229,756

2 Claims. (Cl. 90-151) This invention relates in general to rolls for use in rolling steel rods or the like, and it refers more particularly to the provision of a matrix-like surface marking in the annular grooves or passes for the rod, with a View to embossing upon the rod in the ultimate rolling mill operation a novel type of deformation or surface pattern.

In the manufacture of steel rod of the type used in reinforcing concrete, it is conventional, of course, to pass the rod axially between the rolls of a rolling mill, each pair of rolls having registering peripheral grooves (called passes) which confront one another to receive the rod and form it to the proper cross section. While it is a relatively simple matter to form smoothsurfaced rod in this type of operation by providing smooth passes in the rolls, the use of smooth rod to reinforce concrete leaves much to be desired due to the inadequacy of the bond between the concrete and the smooth surface of the rod.

To overcome the shortcomings of smooth rod it is desirable to provide on the surface thereof irregularities or patterned deformations which, by affording a better bond, will improve the transmission of tensile and axially compressive stresses to the rod when same is embedded in concrete under load conditions; at the same time, however, it is important not to lose sight of the fact that the surface irregularities must be such that they are capable of being formed, in the manufacture of the rod, by reverse master deformations in the pass of the rolling mill roll. There are, in other Words, two basic considerations to be borne in mind in connection with the provision of rod having surface deformations, the first being imposed by limitations inherent in the type of manufacturing process employed and the second growing out of the requirements that must be met in order to obtain optimum bonding and load transmission characteristics when the rod is employed to reinforce concrete.

The solution of this twofold problem by satisfactory correlation of the somewhat opposing factors involved is, broadly speaking, the aim of the present invention.

More particularly, it is the object of the invention to provide a novel method and apparatus for easily, speedily and economically forming in the pass of a rolling mill roll matrix-like master deformations which will permit rods to be rolled in conventional fashion (that is, without introducing any fresh problems in the rolling operation or imposing any limitations thereon) and which, in the rolling operation, will produce on the rods deformations that are effective when the rod subsequently is embedded in concrete to bond the two in a manner excellently suited to obtaining maximum advantage of the tensile and compressive strength of the steel as reinforcement for the concrete.

Another object is to provide in the pass of a rolling mill roll a series of circumferentially spaced transverse grooves, each groove being disposed along the plane nonradial to the axis. of the roll and the planes of the sucvessive grooves being such that in the final rod-rolling 2,788,717 Ice Patented Apr. 16, 1957 operation the ridges or deformations formed on the rod by the grooves lie in parallel planes all similarly inclined relative to the longitudinal axis of the rod; this causes each ridge or deformation to assume the form of a crescent extending slightly less than half way around the rod and it is desired that the circumferential spacing of the aforementioned grooves in the roll be such that the adjacent ridges on the rod overlap slightly due to their inclination, the ends of each crescent being approximately even with the medial section of the next.

From a bonding standpoint, the theoretically ideal ridge or deformation on the rod would be substantially square or rectangular in transverse cross section, i. e., its front and rear walls would extend upwardly from the body of the rod proper approximately at right angles to a surface of the latter. However, there are a number of considerations that militate against such a cross section. in the first place, it would be so exceedingly difficult and expensive to provide in the pass of the rolling mill roll a series of diagonally disposed. crescent shaped grooves of square transverse cross section that for all practical purposes it is out of the question to do so.

Moreover, even if transverse grooves of square cross section could be. provided in the roll, still such grooves could not produce a square tooth or deformation on the rod in the rolling mill operation because the grooves necessarily travel in a. circular orbit with the roll, while the ridges or deformations move with the rod in a straight-line path tangent to that orbit; the movement of the grooves toward and away from the point of tangency produce a wiping or shearing action in the regions just ahead and behind the point of tangency, which action would prevent the formation of a ridge having a square cross section to say nothing of the injurious effect it would have upon the wiping and shearing surfaces of the roll.

An important object of the invention, therefore, is to provide in the pass of a rolling mill roll grooves of modified cross sectional shape which grooves may be produced easily and economically, and, in the rod rolling operation, reduce to a minimum the problems inherent in the aforementioned wiping or shearing action, the deformations formed on the rod by the grooves nevertheless having excellent bonding properties.

While a square tooth or deformation is attractive when we consider only the character of the bond the tooth will make with concrete when the rod is embedded therein, it is much less attractive when we consider also the contribution the tooth makes to the tensile strength of the rod. From the latter standpoint, a square tooth is waste ful of metal since a tooth tapering from a wide root to a narrow crest will increase the tensile strength of the rod move economically and at the same time offer other obvious advantages. In this connection, a feature of the invention resides in the provision in the pass of a rolling mill roll of crescent grooves whose forward and rear walls converge toward the axis of the roll in such a fashion as to produce ridges on the rod having forward and rear faces that, over the major portion of the length of the ridge, form free angles of approximately with the surface of the rod proper. Further than this, it is an important object of the invention to provide tapered grooves of the character indicated whose width across the mouth of the groove is substantially uniform except at the extreme end portions of the groove, whereby, in the rod-rolling operation, the metal of the rod will flow into the groove equally well at all points along its length and thus produce on the rod a deformation of relatively uniform height.

In line with the foregoing aims, it also is an object of the invention to. provide a method and apparatus for forming grooves of the character indicated in the pass of a rolling mill roll; and according to the invention I accomplish this by a novel but simple milling operation which may be carried out speedily, easily and economically. An important feature resides in the arrangement whereby I prevent chattering and jumping of the milling tool and thus make it possible to obtain clean, sharp grooves, while at the same time eliminating injury to the tool and the roll upon which it is working.

A further object of the invention resides in the provision of a milling tool or cutter of novel form which, when used in accordance with the method contemplated, makes it possible to easily and economically produce in the pass of the roll, grooves of the desired character.

Other objects of the invention, together with additional features of novelty whereby the objects are achieved will appear in the course of the following description.

In the accompanying drawings which form a part of the specification and are to be read in conjunction therewith, and in which like reference numerals are used to indicate like parts of the various views:

Fig. l is a vertical cross section through a pair of rolling mill rolls taken along the center line of a pass as indicated by the line 1-1 of Fig. 2, a portion of the rod formed by this pass being shown in side elevation,

Fig. 2 is a sectional elevation taken along the line 22 of Fig. 1, showing a portion of the rod in plan,

Fig. 3 is a cross sectional view of the rod taken along the line 33 of Fig. l in the direction of the arrows,

Fig. 4 is a fragmentary side elevational view of one of the rolls shown in Fig. 1, showing same mounted in a milling machine for the purpose of cutting the transverse grooves or matrix-like master deformations in the passes of the roll,

Fig. 5 is an end elevational View of the machine-androll setaup illustrated in Fig. 4, part of the roll being broken away for purposes of illustration,

Fig. 6 is an enlarged view of the milling tool or cutter, showing same partly withdrawn from the pass of the roll after a grooving operation.

Fig. 7 is a view looking into the pass in the direction indicated by the arrows 77 in Fig. 6, the milling tool being shown in dotted lines,

Fig. 8 is a view of the bottom end of the milling tool,

Fig. 9 is a greatly enlarged cross sectional view of the roll taken approximately along the line 9-9 of Fig. 7, a fragmentary portion of the milling tool also being shown to illustrate the position the tool occupies when it is fully advanced into the pass and ready to be withdrawn after making a cut, and

Fig. 10 is a series of profiles of the cut made by the tool, taken along the radial planes a, b, c, d and e of Fig. 9.

Referring to Fig. l, the confronting portions of a pair of identical rolls are shown in the position they occupy relative to one another during the rod-rolling operation, it being understood that the axes of the two rolls are parallel and fixedly spaced so the confronting peripheral surfaces of the rolls are closely adjacent. Each roll has a plurality of annular grooves or passes 12 which are disposed side by side along the length of the roll and register with corresponding passes in the other roll.

With the rolls turning about their axes in the direction indicated by the dotted arrows, the rod 13 to be formed (or leader bar as it is called in the trade) is fed between the rolls and into one set of passes from the left, emerging on the right formed as shown. The cross section of the leader bar is indicated by dotted lines in Fig. 3 from which it will be evident that the bar is narrower than the pass, while its vertical dimension considerably exceeds the vertical dimension of the pass. Accordingly, as it travels through the pass, the bar is compressed vertically and spreads out laterally, filling the pass and overflowing somewhat at the sides to form the longitudinal beads or overfill 14 on opposite sides of the finished rod. The marginal edges of each pass are chamfered slightly as shown at 16 to assist in the shaping of these beads. The pass proper is of essentially semi-circular cross section (viewed along planes radial to the axis of the roll) that is to say, its shape is such that the core 13 of the finished rod is substantially cylindrical.

The shape and orientation of the deformations 20 formed on the rod will be quite clear from Figs. 1 to 3 and before discussing these features more in detail it will be helpful to describe the method and apparatus by which the master deformations or transverse grooves 22 are formed in the pass of one of the rolls preparatory to using same in the rod-rolling operation.

Referring to Figs. 4 and 5, the roll 10 to be grooved (which it will be understood has previously been provided with the smooth, substantially semi-circular annular passes 12, referred to hereinbefore) is mounted horizontally on the table or work carriage 24 of a milling machine. Conveniently, the roll is supported by means of its trunnions 26 which project axially from opposite ends of the roll and rest in concave cradle-bearings 28 formed in the upper surface of rigid uprights 30 provided on the work carriage of the machine. The trunnions remain seated in these hearings due to the weight of the roll, but the roll can, of course, turn in the bearings about its own axis. However, pivoted to each upright at 32 is a shoe 34, the free end of which may be drawn downwardly as indicated by the arrow, for example by a pneumtaic or hydraulic cylinder 36, to tightly clamp the trunnion and hence hold the roll against rotation. The fluid system for energizing or actuating the cylinder has not been shown, inasmuch as this is conventional and its details form no part of the present invention.

Above the work carriage, the milling machine has a cutter head 38 with a power driven vertical spindle 39 projecting downwardly and carrying the milling tool 40 at its lower end; the latter is mounted in a suitable collet 41. As is conventional in milling machines, the cutter head can be raised or lowered in order that the milling tool may be adjusted to any desired height above the table. Also, when adjusted to any level the head is adapted to travel on horizontal tracks (not shown) in the direction indicated by arrows 42 and 43, which it will be understood causes the axis of the milling tool to move toward and away from roll 10 in a vertical plane perpendicular to the axis of the roll.

In carrying out the milling or grooving operation, the work carriage 24 first is traversed laterally to the left or right (Fig. 4) to bring the pass 12 to be grooved into alignment with the path which the milling tool travels upon the aforementioned movement of the cutter head in the direction of arrows 42 and 43. When the selected pass is in exact register with the path of the tool, the work carriage is locked to prevent further axial shifting of roll 10. Next, head 38 is adjusted up or down until the lower extremity of the milling tool is positioned a predetermined distance above the level of the axis of the roll 10, and then the head is locked against further vertical movement; that the base of the milling tool be elevated exactly the correct distance above the level of the axis of the roll is very important, as will be more evident presently.

Having made the foregoing two adjustments, no change is made in either of them at any time during the milling of the transverse grooves or master deformations 22 in the selected pass.

With the spindle 39 rotating about its vertical axis (Fig. 5), the cutter head 38 now is moved alternately toward and away from'roll 10, as shown by arrows 42 and 43, so that the milling tool advances horizontally into the selected pass 12, attacking the metal at the bottom and sides thereof, and then backs out of the pass. Throughout the time that the milling tool advances into the pass to make its cut and then backs away from its advanced position, cylinder 36 is so energized by means of air or other fluids as to cause shoe 34 to clamp the trunnion 26 and hold the roll against rotary movement. However, as soon as the milling tool has retreated horizontally to a position clear of the pass after making a cut, cylinder 36 is caused to release the downward force that it exerts on shoe 34, and the roll is turned about its axis (see dotted arrow 44) a very small amount, whereupon the roll again is clamped against rotation by means of shoe 34 and cylinder 36; accordingly, the cut made by the tool upon its next advance into the pass will be spaced circumferentially from the last cut, this mode of operation being repeated until the roll has made one complete revolution and the series of cuts made in the selected pass extends all the way around the roll.

In other words, roll is turned step by step about its axis to advance the periphery of the roll in uniform increments, and during the interval that the roll is held stationary after each step, milling tool 4%) is advanced into the pass to cut one transverse groove or master" deformation and then is withdrawn preparatory to advancing the roll another step. When the roll has completed one full revolution and there is an uninterrupted series of uniformly spaced. transverse grooves in the selected pass, carriage 2d of the milling machine is shifted laterally to bring another pass into working alignment with: the milling tool and it then is grooved at. intervals around its circumference following the same procedure, each pass being similarly treated in its turn until. all (or the desired number) of passes have been provided with master deformations.

Because my milling tool travels into and out of the pass in a horizontal direction and because its teeth travel in a horizontal orbit as they cut the sides and bottom of the pass, it will be evident that each. groove is formed along. a generally horizontal plane and may be thought of as following the line of intersection between said horizontal plane and the pass. As the roll turns step by step and the grooves are formed therein successively, no two of them will lie along the same plane, but the planes of all of the grooves will, as a matter of geometry, be tangent to a common (imaginary) cylinder of somewhat smaller diameter than the roll. The diameter of this cylinder is, of course, determined by the distance that the base of my milling. tool is elevated above the level of the aXis of the roll, a matter which will. be dealt with more fully hereinafter; sutiice it to say at this point that the cylinder to which the planes of the respective grooves are tangent should not be less than half nor more than three-quarters of the diameter of the roll itself.

It will be understood that the pneumatic or hydraulic cylinder 36 and the shoe 34 are intended merely to illustrate, by Way of example, one suitable arrangement for alternately holding and releasing the roll for rotation; the same result can be obtained in other ways and with other releasable holding devices, as those versed in the art will readily appreciate. Also, no mechanism has been shown for turning the roll in small increments as discussed above, but this obviously may be done by hand or by suitable mechanical means, the construction of which forms no part of the present invention.

The preferred form of milling tool 40 now will be described with reference to Figs. 6 to 9. Beginning at the constricted neck ida which lies above the cutting region, the body of the tool flares outwardly and downwardly somewhat like a bell, the lower end being notched inwardly at circumferentially spaced intervals to form separate cutting teeth which, of course, are identical to one another. Because of its tapered shape, the diameter of the tool obviously is greatest at its base, and, as may be best appreciated from Figs. 7 and 9, this diameter is substantially equal to the width of the pass across its mouth (disregarding the marginal chamfers 16 for the moment). The width of the pass at this point is but very slightly less than the diameter of the core 18 of the rod to be rolled, so it will be seen that the maximum diameter of the tool approaches very closely the diameter of the final rod.

In view of the foregoing relationship between the diameter ofthe tool and the width of the pass it immediately will be evident that the tool does not cut into the roll beyond the lateral margins of the pass, nor indeed even into the marginal chamfers 16. Its cut at the sides of the pass is relatively shallow as compared to the depth of the finished cut at the bottom of the pass, and it diminishes outwardly to a vanishing point immediately adjacent the chamfers. In addition to certain advantages which this obtains when the roll ultimately is used to roll rod, the arrangement described has the advantage that as the milling tool advances into the pass to make its cut, the orbit travelled by the rotating teeth roughly conforms with the contour of the pass in. the plane which the cut is being made; therefore the cutting aspect of the teeth relative to the work is such that the teeth attack the metal very gradually obviating the possibility of a jump cut or interrupted cut such as would be obtained, for example, were the tool of larger diameter so that its teeth came into sudden contact. at full cutting depth with the metal beyond the lateral margins of the pass. indeed, according to my arrangement the pass acts as a cradle for the tool, resisting any tendency of the tool to jump" as its teeth attack the metal. This feature is of very practical importance in that it makes possible the use of a milling tool. tipped with a very hard but brittle metal such as tungsten carbide, which would be impossible if there were. any jumping or chattering. Also, of course, by resisting chattering it assists in obtaining clean, sharp cuts, as does also another feature which will. be pointed out presently.

The direction of the tools rotation is indicated by the arrows in Figs. 8 and 9, and preferably, though not necessarily, the leading face dill: of each tooth lies in the plane, substantially radial to the axis of rotation. The marginal edges of this face are the cutting edges of the tool. Thus, it will be understood that when the tool rotates, the envelope generated by the teeth is de termined by the profile of the leading face of each tooth and, as is common in tool manufacture, the side and bottom faces that trail rearwardly from a margin of the leading facei. e., rearwardly from the cutting edge are canted slightly inward from the envelope to clear the work at their rearmost edges.

Considering the aforementioned envelope more in detail (since this conforms with, and is perhaps the best way of describing, the shape of the cut the tool is adapted to make) it will be seen that there are actually three major envelope surfaces to be borne in mind. First, the cutting edges 49c travel in an orbital path lying in a plane normal to the axis of rotation. Second, cutting edges 48d are so inclined from top to bottom that, as they travel in an orbit about the tools axis, they may be said to generate or define a frusto-conical envelope inclined at an angle x relative to the vertical. Third, cutting edges 40a are inclined somewhat more, and generate a superposed frusto-conical envelope making an angle y relative to vertical. Angles x and y, of course, also represent the angles that the respective cone surfaces would make with the axis of the tool if they were projected upwardly to meet same.

As previously suggested, the aforementioned envelope surfaces conform with, and in fact determine, the shape of the cut the tool is adapted to make. In other words, referring to the groove cut by the tool as it advances into the pass 12 (Figs. 6 and 7), it will be clear that the cutting edges the of the tool make a fiat bottom cut 220 which is disposed normal to the axis of the tool and hence is a horizontal plane. Edges 40d make a segmento conical cut 22d tapering upwardly from the base cut, and edges 40:: make a smaller segmento conical cut 222 tapering upwardly at a shallower angle. For convenience in distinguishing between them, the larger cut 22d will be referred to as the primary taper and the smaller cut 22s as the secondary taper. The tips of the teeth preferably are bevelled slightly as shown at 40 which produces a small fillet 22 between the base cut 220 and the primary taper 22d.

The size of angle x is quite critical and it has been determined that for satisfactory results this angle should be within the range of approximately to Angle y is somewhat less critical but it will always be greater than angle x and less than 45, best results being obtained if it is in the neighborhood of 30. Assuming that the size of angle x is 10, it will be obvious that the included angle between the base cut 220 and the primary taper 22d is 80. In this case, angle z (Fig. 5) preferably should be 40, or half the size of said included angle. If angle at is larger or smaller than 10, angle 2 should be altered slightly in accordance with the formula By observing the foregoing relationship between angles x and z, a groove always is obtained which, along the median plane of the pass, is a perfect V-that is to say, referring to Fig. 10 (a) which shows the profile of the groove along this plane, a line drawn from the center 0 of the roll through the bottom of the V bisects the angle between the base cut 220 and primary taper 22d, so that angles z and z" are equal to each other (as well as being equal, of course, to angle z). Also, the legs of the V, measured outwardly from the bottom of the V along the diverging walls 220 and 22d are of equal length; and angle r is equal to angle r. Taking into consideration the curvature of the roll, the latter angles are approximately 135 in the case of rolls of average diameter.

Since this symmetry in the cross section profile of the groove 22 along the median line of the pass is achieved only when the foregoing angular relationships are observed, it will be apparent why, as suggested earlier, it is important to maintain the bottom of the milling tool at a predetermined distance above the level of the center 0 of the roll as it travels toward and away from the roll in the milling operation. This vertical distance obviously should be equal to r( sin z) where r is the radial distance from the leading edge of the tool (i. e., the tip of the teeth) to the center of the roll when the tool occupies the forwardmost position to which it is advanced in making a out. Any deviation from the optimum elevation of. the base of the tool above the level of the center of the roll (that is to say, any deviation in the angle z) will cause the tool to produce a groove whose cross section or profile along the median plane of the pass is not perfectly symmetrical. Some slight deviation nevertheless is permissible, but it has been found that, for satisfactory results, angle 2 should always be within the range of approximately 35 to 45 or, to put it differently, the teeth of the milling tool should travel in a horizontal plane which is spaced above the axis of the roll by a distance of not less than half nor more than three-quarters of the radius of the roll.

Apart from the foregoing considerations, the fact that my milling tool travels in a horizontal path that is elevated a considerable distance relative to the center of the roll, has another advantage which is of very practical importance. If the cutting teeth were to be advanced horizontally into the pass at a lower level (for example, along a path approximately level with the horizontal center line of the roll) it would be necessary to employ a tool having a relatively long, slender shank, because, in order to maintain proper clearance between the roll and the moving parts of the milling machine, the teeth of the milling tool would have to be spaced considerably below the lower end of collet 41. With a milling tool having a long shank of this character, it would be ditficult or impossible to prevent the tool from chattering during the milling operation; the cuts would be ragged and imperfect, rather than clean and sharp; damage to, and periodic breakage of, the tool would be unavoidable; and the working rate would be slowed down very materially.

I avoid all of these difficulties and disadvantages because the slope of the roll at and above the point at which my tool enters the pass is such that a tool having a very short shank can be employed, as shown in the drawings. Inasmuch as the cutting teeth are close to collet 41 and very rigidly supported, there is no chattering, the work proceeds rapidly, and clean, sharp cuts are obtained. Contributing to the same desirable end is the fact that the diameter of my tool is so correlated with the width of the pass that the tool is cradled in the pass as it advances and cannot jump laterally, as is discussed hereinbefore.

It will be clear from consideration of the drawings that as my milling tool is advanced horizontally into the pass to make a cut, its first contact with the metal of the roll is made at the outermost tips of the teeth. Cutting therefore begins along the lower portions of the teeth, and as the tool travels slowly forward, the tips of the teeth advance deeper and deeper into the metal of the roll; at the same time the active cutting region of the tool spreads progressively higher and higher along the outer faces of the teeth. The forward travel of the tool preferably is halted when this upward spreading or progression of the cutting region has reached the point illustrated in the drawings, that is to say, when the knee of the tool (i. e., the juncture between the lower slope and the upper slope of the teeth) has reached, but not cut through, the bottom of the pass.

The path traveled by the knee of the tool at the conclusion of its out and just before the tool is backed out of the pass is represented by the lines 22g in Figs. 6, 7 and 9. As will be apparent from these figures, as well as from Fig. 10 (a), no cutting takes place on the upper slope of the teeth where they cross the median plane of the pass. However, on either side of the median plane some cutting does take place on the upper slope, which has the effect of producing a slight undercut or the secondary taper 22c referred to hereinbefore. The extent of the secondary taper may best be appreciated from the profiles shown in Fig. 10.

The part played by the various surfaces of the grooves or master deformations 22 in embossing deformations 20 on the rod when the roll is used in the rolling mill operation will be readily discernible from Figs. 1 to 3. Here it can be seen that the base cut 220 of each groove forms one side 200 of the corresponding deformation; the primary taper 22d forms the major part (20d) of the opposite side and the secondary taper 22c forms the balance (20c) of the latter side.

It will be apparent upon inspection that, from the standpoint of its expanse, the secondary taper 22a is but a small part of each groove; and by the same token, surface 20a of each deformation comprises but a relatively small fraction of the entire deformation surface. Quite obviously, the secondary taper of the groove and the corresponding surface of the deformation could easily be eliminated altogether by a very simple modification of my milling tool, which would merely involve extending the lower slope of the teeth upwardly as indicated by the dotted lines in Fig. 6 and thereby eliminating the upper slope of the teeth. If this were done it will be seen, referring to Fig. 10, that there would be no change in profiles a and e, but that profiles b, c and a would be altered to the extent that the primary taper 22d would extend upwardly to intersect the diagonalline 12a representing the wall of the pass proper, and the width of the mouth of the groove (indicated by the dotted arrow) would be increased correspondingly.

The effect that this would have a es the width of the resultant deformation formed on the rod in a rolling operation is illustrated graphically in Figs. 1 and 2, where the cross-hatched area A represents the shape of the root of my deformation, the projecting portion of the deformation in effect having been cut off flush with the cylindrical surface 18 of the rod; and the dotted line A indicates how the shape of the root would be modified if the surface 202 of the deformation were eliminated and surface 20d extended downwardly in an uninterrupted uniform cone to meet core 18 of the rod.

As will be clear from consideration of the foregoing, the increased upper slope of the teeth of my milling tool has the effect of making the mouth of grooves 22 narrower in the lateral regions of the groove than would otherwise be the case, and consequently, making the root of the deformations narrower in the corresponding regions. This results in crescent shaped deformations whose lines and proportions are more attractive from the standpoint of appearance, but the improvement in the shape of the root of the deformation is not the only, nor even the most important, advantage gained.

The additional advantage may best be appreciated if it is understood, first, that the showing of the deformations in Figs. 1 to 3 is somewhat idealized for the sake of simplicity and clarity. In actual rod rolling practice, the metal of the rod never becomes so plastic and flowable that it will fiow into all of the corners of the grooves 22 and exactly reproduce the shape of the groove; thus under conditions of commercial production, the crest or ridge of each deformation takes the form of a radius curving smoothly from surface 220 to surface 20d, and the latter surface in turn blends smoothly into surface 2th: without any sharp corners.

The extent to which the metal of the rod flows into and fills each groove 22 in the course of the rolling operation is determined largely by the width of the groove across its mouth, and accordingly the quantity of metal entering the groove may vary from point to point along the length of the groove in accordance with variations in the width of this opening. Experience has shown that when the mouth of the groove is wider in the lateral regions than at the center, not only is the root of the resultant deformation wider in those regions (see dotted line A, Figs. 1 and 2) but also the height of the deformation measured outwardly from the core 13 of the rod is proportionately greater in the regions where the root is widest, because the groove or master deformation is more completely filled in those regions; thus, mid-Way between its ends the deformation tends to be both narrower and lower than it is in the lateral regions, giving it a distorted shape which is less attractive than I obtain and, at the same time, less well suited to obtaining the best bond possible with concrete when the rod is embedded therein.

Referring to Fig. 10, it will be seen that by virtue of the form of milling tool I use, i. e., a tool having an upper slope adapted to cut the secondary taper 22e, I obtain a groove or master deformation Whose width across its mouth is such as to overcome the foregoing difficulties. Attention is directed particularly to the fact that the width at the mouth of the groove is virtually the same in the case of profiles a, b and so it may be said that the mouth opening is substantially uniform from the point where profile c is taken (see Fig. 9) to a corresponding point on the opposite side of the pass. The region between these two points corresponds roughly with the lateral thickness of the leader bar 13 that enters the pass in the course of the rod rolling operation (see Fig. 3), which is the critical region so far as obtaining deformations of uniform height is concerned. Because of the uniformity in the mouth or opening of the grooves in this critical region, the metal of the leader bar is forced into the grooves to a uniform depth, and I therefore obtain the attractive and efficient deformation contour indicated in 3', instead of one when; the deformation is rather flat along the top. The contour of the deformation face as seen in Fig. 3 is important in that this represents thebe'ari'ng face through which longitudinal thrust is transmitted to the rodby the concrete in which. it ultimately is embedded; by virtue of the uniform height of the deformation, I obtain an excellent facial distribution of these longitudinal thrust forces and the desired ratio between bearing and shear in the concrete, the importance of which is well appreciated by those versed in, the are! Thus it will be seen that, to beginwith; the deforma tions formed on the rod according to my invention are of very neatand attractive appearance; More important than this, however, is the fact that my deformations make it possible to obtain an excellent bond between the rod and concrete in which the rod-isembedded, achieving an approximate l to 6 ratio'in' bond and shear with the surrounding concrete; Moreover, because the deformations taper to a narrow crest from a rather broad root of relatively uniform width, they increase the tensile strength of the rod very substantially without adding to the rod an amount of metal Which is out of proportion to the gain in strength; as a matter of fact, because the metal of these deformations is very efiiciently employed from the standpoint of strengthening the rod, it will be apparent that the deformations offer an exceedingly economical way of increasing strength and actually conserve metal as compared with other Ways of obtaining a comparable gain in strength.

In addition to these advantages, the design of the deformations is such that no torsional strains are produced Within the rod itself in the course of the rolling operation. Also, the wiping and shearing action which usually takes place between the rolls and the deformations on a rod passing between the rolls is reduced to a minimum, so that there is little more wear on my rolls than would be the case if no deformations were involved, and smooth rod were being rolled.

All of these advantages stern, of course, from the character of the transverse grooves or master deformations 22 I provide in the passes of the rolls, and are the result of my novel method and apparatus for forming said grooves. This involves a simple milling operation which may be carried out rapidly and economically using a standard milling machine; the only special equipment required is the milling tool I have designed and a special carriage for the roll which permits the roll to be alternately clamped and released in order that it may be rotated step by step about its axis, all as described hereinbefore.

From the foregoing it will be apparent that this invention is one well adapted to attain all of the ends and objects hereinbefore set forth, together with other advantages which are obvious and which are inherent to the invention.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the appended claims.

Inasmuch as various possible modifications of the invention may be made without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. A method of preparing a roll comprising the steps of cutting in the roll a circumferential groove or pass which is generally semi-circular in cross-section, then cutting crescent-shaped grooves in the pass, each groove extending transversely of the pass, the convex and concave surfaces of the crescent-shaped grooves being elliptical and the cutting of each crescent being performed by moving a rotating frusto-conical cutter into the groove along a path parallel to but'spaced from a ,diametric plane of the rollwith the base vof the frusto-conical cutter p0- sitioned in said path to. cut at an angle to the radius of the roll thereby creating the elliptical characteristics of the crescent-shaped grooves. Y

2. A method as in claim 1 wherein the distance between the points of the crescent-shaped grooves are substantially equal to the width of the pass at the surface of the roll.

References Cited in the file of this patent UNITED STATES PATENTS 12 Witherow Nov. 30, 1926 Kasley Jan. 18, 1927 Gase Sept. 6, 1938 Galber Jan. 30, 1940 McCarthy Jan. 6, 1942 Drummond Sept. 29, 1942 Manley June 27, 1944 Dettmer June 5, 1945 Aber Jan. 29, 1946 Surerus Sept. 30, 1947 Houk Aug. 15, 1950 FOREIGN PATENTS Germany Nov. 16, 1916 France Sept. 8, 1920 Germany July 25, 1923 Germany Oct. 12, 1936 Great Britain Aug. 2, 1950 

